Project information

Project financing:

Deutsche Forschungsgemeinschaft

Abstract

For the first time, novel Janus nanoparticles (JPs) were used in sufficiently large quantities for
industrial scale blend compatibilization experiments. Several 100 g batches of JPs were
prepared and successfully employed as compatibilizers in technologically relevant poly(2,6-
dimethyl-1,4-phenylene ether)/poly(styrene-co-acrylonitrile) (PPE/SAN) blends. The obtained
small PPE droplet sizes of less than 300 nm (at 10 wt.% JPs in the blend) greatly outperformed
the co-continuous neat blend but also the blend compatibilized with a linear SBM (polystyreneblock-
polybutadiene-block-poly(methyl methacrylate)) triblock terpolymer as benchmark
material. This clearly shows the outstanding performance of JPs as compatibilizers in polymer
blends. Additionally, huge discrepancies in the blend morphology depending on the blending
equipment was found (mini-compounder (g scale) vs. extruder (kg scale)). This demonstrates
the importance of large-scale experiments before considering possible applications. The
optimum JP content, necessary to achieve a homogenous morphology after compatibilization,
was found to be between 2-5 wt.%, which is significantly lower than the amount needed for SBM
triblock terpolymers (10 wt.%).
Fracture mechanics analysis of JP compatibilized blends revealed significantly stronger interface
bonding compared to the neat and SBM compatibilized blends. The JP compatibilized blends
show higher strength and stiffness at the interface compared to the SBM compatibilized blends,
which results in lower toughness of the material when used solely in the blend as
compatibilizers. However, it is possible to tailor the nano/micro structure via a combination of
JPs and SBM triblock terpolymers to tune the macro properties such as toughness. Combination
of JPs with a SBM triblock terpolymer as compatibilizer in the blend resulted in a fine
morphology with small PPE droplets with radius of 100 nm, which homogenized the
deformation in the blend. The toughness as well as resistant against crack growth of the blend
was significantly improved over a wide range of crack propagation rates, revealing the
synergistic effect of a reduced PPE domain size (mediated by JPs) and an elastic interface
(mediated by the SBM triblock terpolymer). Furthermore, understanding the deformation
micromechanisms of each compatibilizer is the key point to design blend morphologies with
tailored mechanical properties.
As an outlook, JPs were also employed in foaming PPE/SAN blends to observe their potential as
highly active foam nucleating agents. The JPs increase the melt strength of the blend and
stabilize the cellular structure with smaller cell sizes. The strong JP mediated linkage at the
interface could also produce homogenous foams with a partially open cellular structure. The
average foam cell size was decreased over 50 % to 900 nm compared to the neat blend and the
minimum foam density reached was 550 kg/m3 (compared to the neat blend with densities of
around 900 kg/m3).